[Radiance-general] HDR

[Kirk Thibault]

Peter and Greg - you guys rock.

Thanks!
------------------------------

Kirk L. Thibault, Ph.D.
kthibault at biomechanicsinc.com

p.  215.271.7720
f.   215.271.7740
c.  267.918.6908

skype. kirkthibault




On Jan 16, 2006, at 12:37 PM, Gregory J. Ward wrote:

> Hi Kirk,
>
> Peter is quick.  He has just set up a new mailing list,  
> hdri at radiance-online.org, which I suggest you subscribe to and we  
> will move the discussion there.
>
> HDRI generation is a separate issue from tone-mapping, and although  
> Photosphere attempts to do both, it only makes a weak effort in the  
> tone-mapping department.  Hdrgen makes no effort to tone-map  
> images, and it should not.  In fact, I don't recommend tone-mapping  
> HDR images into HDR, but directly into the destination display's  
> color space, as an HDR image should maintain it's scene-referred  
> color space.  Some of these issues are discussed and spelled out on  
> hdrsoft's excellent FAQ page:
>
> 	http://www.hdrsoft.com/resources/dri.html
>
> Since you bring up RAW (also discussed by hdrsoft), I should  
> mention that although it is tempting to shoot RAW in preparation  
> for creating HDR images, I have found it not to be helpful in most  
> cases.  The additional range/resolution obtained is modest, and the  
> confusion resulting from the many "development" options you mention  
> means that reproducibility is an issue.  Unless you have a method  
> to go straight from RAW into HDRI, you are better off shooting high- 
> quality JPEGs on most cameras.
>
> I'll make an announcement under a new topic about the HDRI mailing  
> list, and let's continue the discussion there.
>
> -Greg
>
>> From: Kirk Thibault <kthibault at biomechanicsinc.com>
>> Date: January 16, 2006 8:49:46 AM PST
>>
>> IMHO, HDRI may or may not require the color reproduction and  
>> saturation to be as accurate or appealing.  IIt seems to me that,  
>> in general, saturation and color issues are less important when  
>> using a HDRI for image-based lighting than when using the  
>> technique of converting a sequence of LDRI to a single HDRI for  
>> increased dynamic range in a tone-mapped photograph, where the  
>> final output will be an image of the scene as opposed to a light  
>> probe image for IBL.
>>
>> Could hdrgen/Photosphere possibly benefit from more control over  
>> tone-mapping in a way similar to the CameraRaw presents options  
>> for exposing a RAW image?  If the use of HDRI for general  
>> photography (which I am really getting interested in, BTW) would  
>> other users find it useful to expand the ability of hdrgen/ 
>> Photosphere to present the user more control over the tone mapping  
>> process?  This kind of discussion could probably fill a whole new  
>> forum, and I would be all for it, if it is not too much of a hassle.
>>
>> Interesting as always!
>>
>> kirk
>
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